Posted by jb92563 on Friday, February 19, 2010 @ 11:45 AM:
I have posted an online editable spreadsheet with all the different prop size experiments that people have tried.
http://spreadsheets.google.com/ccc?key=0Am_PBsdamZ6gdDZiV3V3NlNlZ2JNZGlHcWw1UDBhTWc&hl=en
You are encoraged to edit this and add more information as you wish.
Apparently, you need a free google account in order to save any data you entered.
So if you don't want to sign up then just post the data in this thread and I'll add it to the spreadsheet.
[Edit by jb92563 on Friday, February 19, 2010 @ 02:04 PM]
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Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org
Posted by jb92563 on Friday, February 19, 2010 @ 12:08 PM:
I am currious as to what prop size Collins culver is?
He seems to be getting the best top speed with a decent climb rate.
Generally you need to be getting 3300+ rpm flat out-level on your prop to also be able to generate
the higher climb rates.
Since HP required to swing a certain diameter is an exponential relationship, you need to minimize drag out near the tips and perhaps the last 20% of the blade.
This can be done by minimizing surface area, minimizing thickness and reducing vortices off the tip.
For my next prop revision I was debating whether to just reduce Dia by an inch or to taper and thin the existing blade out to the tip.
Since I started with a 60" prop the foil is quite thick and wide chord at 54" and will likely benefit significantly by reduced thickness and tapering.
--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org
Posted by Collin on Sunday, February 21, 2010 @ 02:42 PM:
Hi,
I added my prop specs to your chart. One thing tachs, airspeed do very a lot. Also my engine is just over 8-1 compression ratio (std 40hp is 6.6-1, Rectimo 7-1), bigger intake valves, ratio rocker arms, ported heads. I think it all helps a little.
Collin
Posted by jb92563 on Sunday, February 21, 2010 @ 07:22 PM:
Here is my 54x30 Tapered to 1.5" at the tips to increase RPM and reduce drag.
Tests Pending.
Once I get this prop tuned I will retire it and buy a new prop using my test prop as a pattern.
Collin, more HP of your engine will surely give you more in the rpm or thrust department and give you the edge.
Maybe put those engine modifications in the comments field.
Isn't experimental fun?!!!
------------Test Results-------------------------------
[Edit by jb92563 on Monday, March 1, 2010 @ 04:22 PM]
Static ground run: 2850 rpm
Best Climb rate:
Max Level Speed:
Max Level RPM:
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[Edit by jb92563 on Monday, March 1, 2010 @ 04:25 PM]
--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org
